
//236. 二叉树的最近公共祖先
  class TreeNode {
      int val;
      TreeNode left;
      TreeNode right;
      TreeNode(int x) { val = x; }
  }

class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if(root==null){
            return null;
        }
        if(root==p||root==q){
            return root;
        }
        TreeNode leftTree = lowestCommonAncestor(root.left,p,q);
        TreeNode rightTree = lowestCommonAncestor(root.right,p,q);
        if(leftTree!=null&&rightTree!=null){
            return root;
        }else if(leftTree!=null){
            return leftTree;
        }else{
            return rightTree;
        }

    }
}